Microphone



May 13, 1941. HSCHER 2,242,118

MICROPHONE Filed Aug. 23, 1939 2 Sheets-Sheet 1 E. FISCHER MICROPHONE May 13, 1941.

Filed Aug. 23, 1939 2 Sheets-Sheet 2 gzi wmllljfe 26 ln ve ntap Patented May 13, 1941 UNITED STATES PATENT OFFICE MICROPHONE Erich Fischer, Zurich, Switzerland Application August 23, 1939, Serial No. 291,560

Germany August 25, 1938 8 Claims. (Cl. 179-1212) This invention relates to a novel microphone device for the transmission of speech and other sound produced by the human organs of speech.

It is an object of the present invention to provide a microphone which is adapted to transmit speech and the like with a very high degree of efliciency, clearness and freedom from distortion or disturbances.

Another object of the invention is to provide a microphone, of the type referred to, which is of a very small vest-pocket size.

Still another object of the invention is to provide a microphone which when in operation is not noticeable or hardly noticeable by bystanders.

Still another object of the invention is to provide a microphone device by which speech can be transmitted with high emciency while the noise level is transmitted with a reduced intensity.

With these and other objects in view, as may become apparent from the within disclosures, the invention consists not only in the structures herein pointed out and illustrated by the drawings, but includes further structures coming within the scope of what hereinafter may be claimed.

The character of the invention, however, may be best understood by reference to certain of its structural forms, as illustrated by the accompanying drawings in which- Fig. 1 is a longitudinal section through the cavity of the mouth with one embodiment of my novel microphone attached thereto.

Fig. 2 is an exterior view of the same arrangement. 1

Fig. 3 shows the same microphone attachment engaged with the cheek.

Fig. 4 is a perspective view of the microphone device shown in the preceding figures.

Fig. 5 is a diagram showing the electric efiiciency of my novel microphone device. 1.,

Fig. 6 is a plan view of'a modified form of my novel microphone device.

Fig. 7 is a plan view of tion.

Fig. 8 is a side view, partly in section, of still a further modification.

Fig. 9 is an axial section of a modification of the microphone device shown in Figs. 1 to 4.

Similar reference numerals denote similar parts in the diiferent views.

Referring now to the drawings in greater detail, and first to Figs. 1 to 4, it will be seen that the microphone device illustrated in these figures comprises a holder in the form of a a further modificamounting or casing l for a microphone embodied in a cavity thereof. The microphone consists of a stationary or base electrode 3 on the bottom of the cavity and a diaphragm 4 watertightly secured to a collar 5 of the casing, for example, by cementing. The space between the two electrodes is filled up by carbon dust. graphite or any other suitable microphone filling 33. Conductors 6 and I are connectedto the electrodes and pass through suitable channels in the casing and in the U-shaped spring member 8 by which the casing I is resiliently connected with a pressure plate or clip" 9 opposed to the casing I in the position of the microphone device engaged with the check 34. Advantageously, the said U-shaped spring member consists of a resilient U-shaped wire 35 the ends of which are secured in holes in the casing I and counterplate 9 and which is wrapped in a hose or tube 8 of insulating or other .neutral material through which the insulated conductors 6 and I are also passed to the opposite end of the hose, leaving the same in the form of a cable I2 for connection of the microphone to a further transmitting organ, for instance, an amplifier (not shown).

The casing I and the counter-plate 9 advantageously consist of a light neutral insulating material which is chemically inert with respect to the chemical conditions prevailing in the mouth and the human organs of taste. For example, polystyrol may be used for this Purpose which moreover is a good insulator and has very favourable dielectric properties. Also the diaphragm I or at least the outer surface thereof advantageously consists of an inert material or coating. The parts are shown in Fig. 3 in their natural size and it will be noted that the diaphragm 4 has a diameter of about 10 mm. only while the thickness of the whole casing I amounts to about 5 or 6 mm. thus resulting in a total volume of about 1 cubic centimeter only of the microphone parts to be held in the mouth.

Anyway, the said parts will not exceed 1.5 cm! or, in maximum, 3 cm. in volume. While the absolute sensitivity of a microphone of this small size is relatively small, the actual output is still very high, compared to ordinary microphones, due to the favourable transmitting conditions for the speech existing in the cavity of the mouth. The sound intensity is so much higher in the mouth than outside that microphones of the size above referred to are suflicient to produce a reasonable alternating voltage even in case of a small bias. Moreover, due to the absence of any distortions and, more particularly, the reduction of the disturbances due to the outer noise level or the like, the speech current can be amplified very much, if required. Of course, the mouth may be opened for speaking, but still the noise level will be relatively lower in the mouth than outside. The tight acoustic coupling of the microphone with the sound-producing organs is additionally ensured by the mechanical engagement of the microphone body with the parts of the resonant space formed by the cavity of the mouth.

The electrical characteristics of my novel microphone are shown in Figure 5 in which the voltage induced in my mouth microphone by the vowels a," o, u, e" and i is shown by the solid line curves designated with the respective vowels. By way of comparison, the corresponding values of a microphone of a normal size and sensitivity arranged in the immediate vicinity of the mouth, but outside thereof, are indicated in the same diagram with dot and dash lines. The noise level is shown to be approximately the same for both microphones, in the case of half open lips and without speech, as indicated by the dotted horizontal line. Of course, in case of very high noise levels in the room, the voltage produced thereby in my microphone arranged in the mouth will be less than that induced in a microphone arranged outside the mouth. Moreover, as clearly shown in the diagram, the voltage produced in my microphone is so much higher than that produced by the normal microphone that the amplification factor for my microphone may be considerably reduced to reduce the noise level accordingly. In other words, the "signalto-noise" ratio of my microphone is much more favourable.

While the attaching means for my novel microphone as shown in Figs. 1 to 4 will be very suitable in most instances of practical application, it is also contemplated, within the purview of my invention, to provide the microphone holder with modified attaching means such as shown, for example, in Figs. 6 to 8.

Referring first to Fig. 6, a microphone i3 is installed in a base plate ll of the type used as a base for dental prosthesis fitted with clasps ii for engagement with the teeth l6. Fig. 7 shows a modification comprising a microphone holder 11 fitted with clasps II for engagement with the teeth ii. In both modifications shown in Figs. 6 and 7 the cable It serving for the connection of the microphone to the further transmitting organs may be led out of the mouth in a similar manner as indicated in Figs. 1, 2 and 3.

Where it is intended to apply and remove the microphone from the mouth very easily and to camouflage the same, a microphone 2| may be arranged across the mouthpiece II of a body in the form of a pipe 22 as shown in Fig. 8, from which a connecting cable 23 comes out at any suitable point. In order to permit speaking without being hampered by the pipe a clasp 24 may be provided at the mouthpiece thereof for engagement by the teeth as the same are closed so as to hold the pipe in position as the mouth is opened for speaking. If desired, an amplifier, battery or spare microphone set 31 may be arranged in the bowl of the pipe.

As shown in Fig. 9 on an enlarged scale, the microphone proper may be in the form of a separate self-contained unit comprising a box 25 which can be easily engaged in and detached from a recess of the microphone holder 26.

The said microphone box may be protected by a perforated cap 21 engaged between the box and the recess in the holder to prevent the tongue from touching the microphone and to prevent the spittle from entering the microphone. The said cap may be covered by a layer of sponge rubber 28 as indicated. The two connecting wires 32 pass through a groove 29 in the holder which is closed by a wedge or other closure strip 30. A spring wire 35 which corresponds to the U- shaped wire 35 in Figs. 1 to 4 is tightly secured in the holder and enclosed in a rubber hose or the like 8 together with the wires 32.

The holder 26 may consist of a suitable light and tasteless insulating material, such as, Polystyrol, artificial resin, condensation products of urea and formaldehyde and the like. If desired, elastic materials may be used. An exchangeable cover 36 of rubber or the like may be stripped over the microphone by every user thereof to avoid the inconveniency for different persons to take the same microphone into their mouth.

The method andapparatus of the present invention have been described in detail with reference to specific embodiments. It is to be understood, however, that the invention is not limited by such specific reference but is broader in scope and capable of other embodiments than those specifically described and illustrated in the drawings.

I claim:

1. A microphone device for the transmission of speech from the human organ of speech, comprising a microphone and a holder for said microphone, said microphone and holder being shaped and dimensioned to permit unhampered speaking when inserted in the cavity of the mouth, and clamping means for detachably securing said holder on the inner face of the check.

2. A microphone device for the transmission of speech from the human organ of speech, comprising a microphone and a holder for said microphone, said microphone and holder being shaped and dimensioned to permit unhampered speaking when inserted in the cavity of the mouth, and a spring clip for clamping said holder to the inner face of the cheek.

3. A microphone device for the transmission of speech from the human organ of speech, comprising a microphone and a holder for said microphone, said microphone and holder being shaped and dimensioned to permit unhampered speaking when inserted in the cavity of the mouth, and a spring clip for clamping said holder to the inner face of the cheek, said clip including also the electric connection of the microphone with the further transmitting organs.

4. A microphone device for the transmission of speech from the organ of speech of a person using said microphone device, comprising a microphone having a volume of not more than 3 cubic centimeters, a holder for said microphone, clamping means for detachably securing said holder within the cavity of the mouth of said person, for holding the microphone in a favourable position for receiving the sounds produced by the organ of speech of said person, and means for transmitting the speech currents produced in said microphone to a point outside said person.

5. A microphone device for the transmission of speech from the organ of speech of a person using said microphone device, comprising a carbon microphone having a volume of not more than 3 cubic centimeters, a holder for said microphone, clamping means for detachably securing said holder within the cavity of the mouth 0! said person, for holding the microphone in a favourable position for receiving the sounds produced by the organ of speech of said person, and means for transmitting the speech currents produced in said microphone to a point outside said person.

6. A microphone device for the transmissio of speech from the organ of speech of a person using said microphone device, comprising a carbon microphone, a holder for said microphone, clamping means for detachably pressing said holder against inner part of the cavity of the mouth of said person, for holding the microphone in a favourable position for receiving the sounds produced by the organ of speech of said person, and means for transmitting the speech currents produced in said microphone to a point outside said person.

7. A microphone device for the transmission of speech from the organ of speech of a person using said microphone device, comprising a microphone, a holder for said microphone, and

clamping means for detachably securing said holder within the cavity of the mouth of said person, for holding the microphone in a favourable position for receiving the sound produced by theorgan of speech of said person, said holder and said clamping means including a channel for for holding the microphone in a favourable position for receiving the sounds produced by the organ of speech of said person, and'means for transmitting the speech currents produced in said microphone to a point outside said person,-

said microphone and holder being shaped and dimensioned to permit unhampered speaking when inserted in the cavity of the mouth.

ERICH FISCHER. 

